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alimentary canal

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Oesophagus Stomach lub The Histology of the mammalian alimentary canal For Mr Elvin Love By Jaenette Satherlund 26/10/2007 Alimentary canal The alimentary canal is a long muscular tube starting at the mouth and ends in anus. It is the process from ingestion to egesting (or expelled residues). Below is a description of the adaptation in the different parts of the alimentary canal. Oesophagus Oesophagus is the start of the alimentary canal. There are different layers though out the oesophagus. The lining in the oesophagus is called epithelium. The epithelium runs through the whole alimentary canal but in the oesophagus the epithelium is stratified squamous it is characterised by its scale like cells. These types of lining are vital for the oesophagus as it is constantly exposed to digestive enzymes and movement of food. New cells are constantly produced in the epithelium stratified squamous to replace the cells that are depleted by the moment of food. To protect the oesophagus further the epithelium produce mucus. Mucus is a slimy liquid that lubricate and protect the epithelium against damage. It also protects the oesophagus against digestive enzymes. There is no digestive enzyme secreted in the oesophagus. The only digestive enzyme comes from the salivary glands. They produce digestive juice that contains the enzyme amylase. Salivary glands are based under the tongue and transport saliva via ducts to the mouth. Saliva contains amylase that starts the process of breaking down cooked starch into maltose. ...read more.


When food has broken down to liquid the pyloric sphincter releases the liquid little at the time to the duodenum. Duodenum: duodenum is the first part of the small intestine. Most of digestion and absorption happens in the small intestine. The duodenum receives digestive enzymes from pancreas, pancreatic glands. (The enzymes are not active until they reach duodenum). The pancreatic juice contains sodium hydrogencarbonate, this is vital as the sodium hydrogencarbonate neutralizes the acid from the stomach, and enzymes don't work well in acidy conditions. The pancreatic juice acts on all types of food. The duodenum also receives bile; it is produced in the liver and stored in the gall bladder. It is then pored in to the duodenum via ducts. The pancreatic juices enzymes are attacking all types of food. The bile assist in the process of dissolving fats. This gives the enzyme lipase a better surface to work on so the fat can be absorbed of the lining in the duodenum. The mucosa has adapted in the duodenum to maximise the intake of the absorption. The lining in the duodenum is a thin simple columnar epithelium covered by villi. They are finger or leaf like projections. They are 0.5mm in length, at the surface of each of the villus are fine hair called microvillus. The villus has specialised in absorbing food and, with the microvillus the surface is extended further. In the villus there are a fine network of capillaries transporting blood. ...read more.


The duodenums epithelium is considerably thinner so the products can easily pass to the capillaries in the villi. The duodenum also produce sodium hydrogencarbonate neutralize acid from the stomach. The Brunner's gland contains goblet cells that produce mucus to further protect the epithelium. The duodenum has a complicated blood system that transports the blood to the liver for filtering the blood before the blood enters the rest of the body. Ileum specific adaptation: The villi in the ileum are narrower and the crypts are as deep as in the duodenum. But the ileum itself is much longer; it also has spiral rings throughout the whole ileum and effective villus. The villi are constantly shed in the lumen rapid cell division in the epithelium replaces the lost cells. The villi constantly renew them self and keep the epithelium health and effective. Each villus contains a lacteal that are a capillary of the lymphatic system that transport fat. The ileum also has paneth cells that protect the body from getting ill. Conclusion: throughout the whole alimentary canal there are fundamentally similarities: The alimentary canal has epithelium, mucosa, muscularis mucosa, submucosa, circularmuscle, longitudinal muscle (together they are external muscular coat) and serosa. Other similarities are secreting mucas cells and peristalsis. The different part of the digestive system has adapted to make sure food is not damaging the alimentary canal and maximise the nutrion intake with many more important tasks. All this is done so we can function. Source: GCSE biology third edition www.lab.anhb.edu.au www.refernnce.com www.medic8.com ...read more.

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